ZnO-Enhanced Reduced Graphene Oxide Electrodes from Cocoa Shell: Nanoarchitectonics Platform for Photoelectrocatalytic Detection of Methylene Blue.

In this study, we report the successful preparation of reduced graphene oxide modified zinc oxide (rGO-ZnO) composites from cocoa shells. Synthesis of rGO-ZnO was carried out using the Hummer method and thermal reduction. The electrode material was comprehensively characterized using fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy & Energy Dispersive X-ray (SEM-EDX). The photoelectrocatalytic performance of the prepared composite electrodes was evaluated using various electrochemical techniques, including Linear Sweep Voltammetry (LSV), Cyclic Voltammetry (CV), and Multi Pulse Amperometry (MPA). The FTIR analysis of rGO-ZnO exhibited distinct bands corresponding to C-O at 1022 cm-1, C=C at 1600 cm-1, and Zn-O at 455 cm-1. The XRD analysis revealed characteristic peaks at 26.6º, 29.2º, 36.2º, 44.04º, 47.58º, and 64.4º, confirming the presence of key crystalline phases. SEM-EDX analysis of rGO-ZnO revealed a rough surface morphology with bright white and black regions, signifying the coexistence of ZnO and rGO with carbon, oxygen, and zinc contents of 78.98%, 17.46%, and 3.56%, respectively. The investigations involved the photoelectrochemical profiles of methylene blue organic dyes at different concentrations, ranging from 0.5 ppm to 3.0 ppm. The acquired findings offer valuable understanding into the photoelectrocatalytic effectiveness of the composite electrodes containing rGO-ZnO, suggesting their potential use in potential scenarios involving the revitalization of the environment in industrial water systems.

Antioxidant Activity of Usnic Acid Compound from Methanol Extract of Lichen Usnea sp.

Lichen Usnea sp. is one of the sources of natural bioactive compounds which are currently being developed as medicinal ingredients. The purpose of this study was the isolation and identification of secondary metabolites from methanol extract, toxicity test and antioxidant activity of Usnea sp. Lichen was isolated by maceration using methanol solvent, then separated by liquid-liquid partition and separation using vacuum chromatography. Based on the results of the study, NMR-1D spectral data and FTIR spectrum is the presence of functional groups showed the presence of F15 compound is usnic acid consisting of 18 carbons with 3 carbons from the C=O carbonyl group. The results of the toxicity test showed that all of them were active against Artemia salina L. shrimp larvae with LC50 values of 0.820 µg/mL (Usnea sp.), 1.030 µg/mL (n-hexane), 1.056 µg/mL (ethyl acetate), and 1.236 µg/mL (methanol extract). The results of the antioxidant activity test showed that the inhibitory activity of usnic acid isolate was very active with an IC50 value of 11.696 µg/mL. Meanwhile, methanol extracts and ethyl acetate showed antioxidant activity with IC50 values of 18.098 and 26.917 µg/mL, respectively.

Potential of Usnic Acid Compound from Lichen Genus Usnea sp. as Antidiabetic Agents.

Lichen Usnea sp. is potential as a new natural medicine. This study report isolation of secondary metabolites from lichen Usnea sp. and α-glucosidase inhibitory, which is potential as an antidiabetic agent. Lichen powder was macerated using methanol, separated using column chromatography gravity and thin-layer chromatography. The crystalline was isolated and purified by the recrystallization process for obtaining pure compound. The isolated compound was determined using FTIR and NMR spectroscopy (1H and 13C). The results showed that the isolated compound was yellow needle crystals. Based on the spectra data interpretation, it was obtained usnic acid compound with the molecular formula of C18H16O7. The α-glucosidase inhibitory activity test showed that the usnic acid had activity in inhibiting the α-glucosidase enzyme with an IC50 value of 106.78 µg/mL. The usnic acid from Usnea sp. has a very good impact on the source of natural compounds as an antidiabetic drug in the future.

Effectiveness of Green Chemical Solvent-based on Triethylammonium Methanesulfonate Ion Liquid for the OPEFB Pretreatment Process.

Many studies have explored the pretreatment of lignocellulosic biomass based on oil palm empty fruit bunch (OPEFB) which is categorized as potential biomass waste for bioethanol production. Before proceeding further to obtain bioethanol, several steps such as pretreatment to increase organic constituents are needed. The ionic liquids (ILs) were commonly investigated by many researchers for lignocellulosic pretreatment because it is easy solubilization property, non-toxic, and not harmful impacts on the environment. Therefore in this study, the hypothesis and main objective were to observe the effectiveness of triethylammonium methanesulfonate ion liquid (TMS IL) in the OPEFB lignocellulose pretreatment process. Three variations were studied to obtain optimization of the pretreatment process, such as times duration, IL composition, and temperature. Based on these results, we observed the effectiveness of the time duration for OPEFB pretreatment of 20 hours. Furthermore, it was applied to determine the optimization of IL composition and temperature showing that using 91% (1:1:10) at 120°C for 20 hours has provided good performance for the OPEFB lignocellulose pretreatment process. TMS IL has exhibited the ability to reduce hemicellulose and lignin contents to 7.35% and 17.80%, whereas cellulose was increased by 54.24%. This has the opportunity to be projected to a larger scale for bioethanol production based on OPEFB lignocellulose.

Optimization of OPEFB lignocellulose transformation process through ionic liquid [TEA][HSO4] based pretreatment.

Research on the transformation of Oil Palm Empty Fruit Bunches (OPEFB) through pretreatment process using ionic liquid triethylammonium hydrogen sulphate (IL [TEA][HSO4]) was completed. The stages of the transformation process carried out were the synthesis of IL with the one-spot method, optimization of IL composition and pretreatment temperature, and IL recovery. The success of the IL synthesis stage was analyzed by FTIR, H-NMR and TGA. Based on the results obtained, it showed that IL [TEA][HSO4] was successfully synthesized. This was indicated by the presence of IR absorption at 1/λ = 2814.97 cm-1, 1401.07 cm-1, 1233.30 cm-1 and 847.92 cm-1 which were functional groups for NH, CH3, CN and SO2, respectively. These results were supported by H-NMR data at δ (ppm) = 1.217-1.236 (N-CH2-CH3), 3.005-3.023 (-H), 3.427-3.445 (N-H+) and 3.867 (N+H3). The TGA results showed that the melting point and decomposition temperature of the IL were 49 °C and 274.3 °C, respectively. Based on pretreatment optimization, it showed that the best IL composition for cellulose production was 85 wt%. Meanwhile, temperature optimization showed that the best temperature was 120 °C. In these two optimum conditions, the cellulose content was obtained at 45.84 wt%. Testing of IL [TEA][HSO4] recovery performance for reuse has shown promising results. During the pretreatment process, IL [TEA][HSO4] recovery effectively increased the cellulose content of OPEFB to 29.13 wt% and decreased the lignin content to 32.57%. The success of the recovery process is indicated by the increasing density properties of IL [TEA][HSO4]. This increase occurs when using a temperature of 80-100 °C. The overall conditions obtained from this work suggest that IL [TEA][HSO4] was effective during the transformation process of OPEFB into cellulose. This shows the potential of IL [TEA][HSO4] in the future in the renewable energy sector.

Examination the Hydrolysis Feasibility of OPEFB Biomass Using Aspergillus niger as Cellulase Enzyme-producing Fungus.

The objective of this study was to obtain optimization results from the biological hydrolysis of Oil Palm Empty Fruit Bunches (OPEFB) using Aspergillus niger (A. niger) BIOTROP 2173 isolated from grain. Optimized hydrolysis parameters include temperature, pH and time. The hydrolysis process was carried out by growing A. niger on OPEFB powder (± 30 mesh) through two schemes, namely hydrolysis on OPEFB pretreatment with 10% NaOH and hydrolysis on OPEFB non-pretreatment. The optimization results show that the best hydrolysis process of A. niger BIOTROP 2173 occurs in OPEFB pretreatment. The optimum conditions for temperature, pH and time obtained are 40°C, 6 and 24 hours, respectively. Although the amount of reducing sugar produced was lower than the OPEFB non-pretreatment, the performance of the cellulase enzyme during the hydrolysis process of OPEFB pretreatment was very good, with a fast hydrolysis rate. These results indicate that the performance of A. niger BIOTROP 2173 in the hydrolysis process is influenced by the pretreatment stage. The optimum conditions obtained then became a reference in the production of reducing sugar based on A. niger BIOTROP 2173. The amount of reducing sugar produced from OPEFB pretreatment was 0.94 mg.mL-1, while for OPEFB non-pretreatment was 15.83 mg.mL-1.